Green dock leaf beetles

 There are lots of broad-leaved dock Rumex obtusifolius plants around at the moment with foliage that looks like this, resembling green lace.

It's the handiwork of the larvae of the green dock leaf beetle Gastrophysa viridula - turn over a leaf where damage is just beginning and you'll find several on the underside, eating the soft tissue between the leaf veins. When fully fed they burrow down into the soil and pupate, emerging as adult beetles within a couple of weeks.

And here are the rather beautiful adult leaf beetles, mating. The abdomen of the female is so distended with eggs that it displaces her wing cases. She'll lay as many as 1000 eggs and, with a short generation time, the numbers of these insects can rise rapidly as summer progresses.

Green Dock Leaf Beetles

I found scores of these green dock leaf beetles Gastrophysa viridula mating on dock leaves in the pastures beside the River Towy near Carmarthen earlier this week. The larvae chew holes on the dock leaves then pupate in the soil. In a good year they can produce three generations.

The beetles have beautifully iridescent exoskeletons which change from metallic green to bronze depending on the angle of the light. A single female can lay up to 1000 eggs. For the males, finding a female to mate with is highly competitive. In the top picture you can see two males confronting one another over a female.....

... and in this picture you can see a startling case of coitus interruptus, where a mating male - still coupled to the female - has been dragged off her by a rival. I thought this sort of thing only went on in the Bigg Market in Newcastle on a Friday night.....